Various storage hardware vendors have introduced features on their disk arrays to allow the movement of storage volumes both within a single array and between arrays. These features were mostly designed as high availability features and not targeted as data migration features. In addition many operating system (OS) vendors have developed mirroring software which allowed synchronous writes to a secondary volume. Again these were designed with high availability in mind, rather than data migration.
Recently, a standard set of tools has been provided by storage and operating system vendors and other software developers to allow data to be automatically copied, archived, and restored. Although some progresses have been made, a problem still exists in that the availability capabilities of these facilities have not kept pace with the availability requirements that exist in data centers. A storage administrator has to support the increasing demands of continuous 24 hour by 7 day data availability.
There is an explosive growth in the need to store and have on-demand access to greater and greater pools of data. As capacity requirements skyrocket, data availability demands increase. These factors coupled with the need to control costs dictate that new storage technology be implemented. The dilemma faced by data center management is that the implementation of new storage technology is disruptive and therefore conflicts with the need to maximize availability of the data. Therefore, an additional tool is required that will allow data to be non-disruptively relocated or migrated within the data center.
Typically, a data migration facility provides the ability to “relocate” data from one device to another device. A logical relationship is defined between a device (e.g., the source) and another device (e.g., the target). The logical relationship between a source and target volume provides a framework for a data migration. The data migration facility controls multiple concurrent migrations. A migration is a process that causes the data on the source volume to be copied without changing to the target volume.
Migration facilities that exist today were primarily designed for disaster recovery or the facilities were meant to address single volume failures. Many volume managers today allow mirrors of logical volumes to be created on a server. The actual method and commands to create mirrors varies by a volume manager. Continuous read and write accesses by applications are allowed during the data migration process and all data updates are reflected to the secondary volume. Logical volume mirrors were designed for high availability and although they can be used to migrate volumes from one control unit to another, they are not optimized for data migration purposes.
Recently, some vendors have introduced array based mirroring techniques. However, such techniques have been designed for proprietary systems. A user has to install a specific tool from the specific vendor in order to utilize such a system. Thus, the products that are available on the market today do not meet all of the data migration requirements.